Chevy LS2 and Trans??? any real issues besides weight

Hey guys i'm a new pilot that really wants to build his own craft. help
me with this one issue.

I want to use a chevy ls2 or ls7 as the power plant in my craft.
now looking at everything including the hp/torque curves i've decided
running the engine around 3100 rpm should give me around 250 hp with
good torque now getting that power to a propeller seems to be an issue.
I'm wondering besides weight would there be any real issue using the
associated transmission locked in gear maybe 3rd/4th/5th gear whichever
is just under 1:1.

it would seem the car tranny has been engineered to convert the engine
motion into the spinning i would need to propel the propeller. plus
running the engine at 3100 rpm it would prob last longer than i will.

the aircraft i want to design is a very cab foward design with a
pusher prop and the engine would be mounted approx mid craft.

i'm new at this and besides having an engineering background i really
have no exp building an aircraft so any opinions would be helpful

thanx

Mrv